Each month, anyone who wants to trade bases can email crew planning/staffing with their current and desired base. The list is published close to real time so you can see who wants to trade where. You cannot trade seats/equipment, just bases. In seniority order, opposite requests are matched, so that the end result is the same number of people remain in each BES, and no training events are generated (except any special qual associated with the new base). If you base trade, all remaining vacation you have is dumped into open time. Also, if you’re holding a bid award ( even if it is for say a 12 month out transfer date)…you aren’t permitted to trade. So let’s say tomorrow the award comes out for the annual bid, and I get awarded LAX effective 12/1/2022, I can’t trade between now and then to LAX. I have to stay put until my transfer date. Meanwhile, someone junior to me could base trade in there if there was an opposite trade request in.

So seniority is honored since the base trade occurs in seniority order on a monthly basis, but only with regards to opposite trade requests. If only one person wants to trade MCO-JFK, but 3 people want JFK-MCO, the senior one gets it. So, it is definitely possible to trade into a base you can’t hold depending on the trading. A guy in LGB traded into LGB long before he could hold it, and a guy senior to him had forgotten to put his trade request in that month (it’s a monthly email you have to send in for each month’s trade, and he forgot the one month an opposite request came in), causing some consternation. But regardless, there is some seniority required to make to work.

Where it doesn’t honor seniority is say the senior LGB FO who could hold CA in another base but not in LGB, but a more junior guy goes to JFK to upgrade, then he base trades in before the more senior guy takes it on a bid. The guys who risked upgrade/commute to JFK for an undetermined amount of time got in, while he (more senior) who stayed put as an FO didn’t. Another scenario, say a more senior guy is a BOS 320 CA and wants MCO 320 CA, and there’s a more junior JFK 320 CA who wants MCO 320 CA, if there’s a MCO 320 CA who wants JFK 320 CA, the seniority doesn’t matter for the JFK/BOS guys—only the guy with the opposite trade request can get it.